Wearable Chemical Sensors Research Articles

Optically Sintered 2D RuO2 Nanosheets: Temperature‐Controlled NO2 Reaction

2D Ru oxide nanosheets (NSs) with optically punched nanoholes are synthesized and integrated on a flexible heating substrate, i.e., silver nanowire (Ag NW)‐embedded colorless polyimide (cPI) film, for application in wearable chemical sensors. Multiple discrete pores on the sub‐5‐nm scale are formed on the basal planes of Ru oxide NSs by irradiation of intense pulsed light. The chemical sensing characteristic of the porous Ru oxide NSs toward nitrogen dioxide (NO2) is investigated under controlled temperatures by applying DC voltage to the Ag NW‐embedded cPI film. The improved NO2 responding and recovery kinetics are achieved using the porous Ru oxide NSs with sensitivity of 1.124% at 20 ppm at a film temperature of 80.3 °C. A wireless patch‐type sensor module is developed to demonstrate wearable sensing of NO2 using the Ru oxide NSs on Ag NW‐embedded cPI heating film. This work paved the new way for application of atomically thin and porous Ru oxide NSs in chemical sensors, which can detect hazardous species in real time.

Transparent, flexible, and stretchable WS2 based humidity sensors for electronic skin.

Skin-mountable chemical sensors using flexible chemically sensitive nanomaterials are of great interest for electronic skin (e-skin) application. To build these sensors, the emerging atomically thin two-dimensional (2D) layered semiconductors could be a good material candidate. Herein, we show that a large-area WS2 film synthesized by sulfurization of a tungsten film exhibits high humidity sensing performance both in natural flat and high mechanical flexible states (bending curvature down to 5 mm). The conductivity of as-synthesized WS2 increases sensitively over a wide relative humidity range (up to 90%) with fast response and recovery times in a few seconds. By using graphene as electrodes and thin polydimethylsiloxane (PDMS) as substrate, a transparent, flexible, and stretchable humidity sensor was fabricated. This senor can be well laminated onto skin and shows stable water moisture sensing behaviors in the undeformed relaxed state as well as under compressive and tensile loadings. Furthermore, its high sensing performance enables real-time monitoring of human breath, indicating a potential mask-free breath monitoring for healthcare application. We believe that such a skin-activity compatible WS2 humidity sensor may shed light on developing low power consumption wearable chemical sensors based on 2D semiconductors.

Wearable Sensors: Silver Nanowire Embedded Colorless Polyimide Heater for Wearable Chemical Sensors: Improved Reversible Reaction Kinetics of Optically Reduced Graphene Oxide (Small 42/2016)

Wearable Sensors: Silver Nanowire Embedded Colorless Polyimide Heater for Wearable Chemical Sensors: Improved Reversible Reaction Kinetics of Optically Reduced Graphene Oxide (Small 42/2016)

Silver Nanowire Embedded Colorless Polyimide Heater for Wearable Chemical Sensors: Improved Reversible Reaction Kinetics of Optically Reduced Graphene Oxide.

Optically reduced graphene oxide (ORGO) sheets are successfully integrated on silver nanowire (Ag NW)-embedded transparent and flexible substrate. As a heating element, Ag NWs are embedded in a colorless polyimide (CPI) film by covering Ag NW networks using polyamic acid and subsequent imidization. Graphene oxide dispersed aqueous solution is drop-coated on the Ag NW-embedded CPI (Ag NW-CPI) film and directly irradiated by intense pulsed light to obtain ORGO sheets. The heat generation property of Ag NW-CPI film is investigated by applying DC voltage, which demonstrates unprecedentedly reliable and stable characteristics even in dynamic bending condition. To demonstrate the potential application in wearable chemical sensors, NO2 sensing characteristic of ORGO is investigated with respect to the different heating temperature (22.7-71.7 °C) of Ag NW-CPI film. The result reveals that the ORGO sheets exhibit high sensitivity of 2.69% with reversible response/recovery sensing properties and minimal deviation of baseline resistance of around 1% toward NO2 molecules when the temperature of Ag NW-CPI film is 71.7 °C. This work first demonstrates the improved reversible NO2 sensing properties of ORGO sheets on flexible and transparent Ag NW-CPI film assisted by Ag NW heating networks.

Textile Organic Electrochemical Transistors as a Platform for Wearable Biosensors.

The development of wearable chemical sensors is receiving a great deal of attention in view of non-invasive and continuous monitoring of physiological parameters in healthcare applications. This paper describes the development of a fully textile, wearable chemical sensor based on an organic electrochemical transistor (OECT) entirely made of conductive polymer (PEDOT:PSS). The active polymer patterns are deposited into the fabric by screen printing processes, thus allowing the device to actually “disappear” into it. We demonstrate the reliability of the proposed textile OECTs as a platform for developing chemical sensors capable to detect in real-time various redox active molecules (adrenaline, dopamine and ascorbic acid), by assessing their performance in two different experimental contexts: i) ideal operation conditions (i.e. totally dipped in an electrolyte solution); ii) real-life operation conditions (i.e. by sequentially adding few drops of electrolyte solution onto only one side of the textile sensor). The OECTs response has also been measured in artificial sweat, assessing how these sensors can be reliably used for the detection of biomarkers in body fluids. Finally, the very low operating potentials (<1 V) and absorbed power (~10−4 W) make the here described textile OECTs very appealing for portable and wearable applications.

Ultrafast optical reduction of graphene oxide sheets on colorless polyimide film for wearable chemical sensors

Ultrafast reduction of graphene oxide sheets was achieved by intense pulsed light irradiation on a highly transparent and thermally stable polyimide substrate. The obtained reduced graphene sheets exhibited improved chemical sensing characteristics, which are promising in wearable chemical sensors for real-time environmental monitoring.

Special Issue for Wearable Electrochemical Sensors

Wearable sensors have garnered considerable recent interest in recent years owing to their tremendous promise for a wide range of healthcare, fitness or military applications. These wearable sensing platforms provide new avenues to monitor individuals continuously and can thus provide rich real-time information regarding a wearer's health and performance. While most early efforts on wearable fitness and biomedical devices have been devoted to the continuous monitoring of vital signs (such as heart rate, respiration rate, skin temperature) from physical signals, wearable chemical sensors have received limited attention. The recent introduction of new non-invasive chemical sensors aims at filling current gaps in wearable sensor technology, as desired for mobile health monitoring and remote diagnostics. Wearable electrochemical sensors have been integrated recently onto both textile materials and directly on the epidermis for various monitoring applications owing to their unique ability to process chemical analytes in a non-invasive and non-obtrusive fashion. These recent efforts have led to tremendous attention to body-worn electrochemical devices, including potentiometric electrolyte sensors and amperometric biosensors for metabolites. The successful realization of wearable sensing devices requires the migration of electrochemical systems from traditional rigid and planar substrates to flexible, wearable, and conformal sheets. The field of wearable electrochemical sensors offers exciting collaborative opportunities and its future growth and success will rely on the abilities of the researchers to continue to innovate and collaborate to address the existing challenges and opportunities. The present Special Issue of Electroanalysis sheds useful insights into the latest advances and current trends in the field of wearable electrochemical sensors and biosensors. Given the rapid development of such body-worn sensors, the studies reported in this Special Issue are just the beginning of a fantastic topic and journey. I would like to thank all the authors who contributed to this issue. Joseph Wang, Chief Editor

Wearable Chemical Sensors: Present Challenges and Future Prospects

Wearable sensors have received considerable interest over the past decade owing to their tremendous promise for monitoring the wearers’ health, fitness, and their surroundings. However, only limited attention has been directed at developing wearable chemical sensors that offer more comprehensive information about a wearer’s well-being. The development of wearable chemical sensors faces multiple challenges on various fronts. This perspective reviews key challenges and technological gaps impeding the successful realization of effective wearable chemical sensor systems, related to materials, power, analytical procedure, communication, data acquisition, processing, and security. Size, rigidity, and operational requirements of present chemical sensors are incompatible with wearable technology. Sensor stability and on-body sensor surface regeneration constitute key analytical challenges. Similarly, present wearable power sources are incapable of meeting the requirements for wearable electronics owing to their l...

A wearable fingernail chemical sensing platform: pH sensing at your fingertips

This article demonstrates an example of a wearable chemical sensor based on a fingernail platform. Fingernails represent an attractive wearable platform, merging beauty products with chemical sensing, to enable monitoring of our surrounding environment. The new colorimetric pH fingernail sensor relies on coating artificial nails with a recognition layer consisted of pH indicators entrapped in a polyvinyl chloride (PVC) matrix. Such color changing fingernails offer fast and reversible response to pH changes, repeated use, and intense color change detected easily with naked eye. The PVC matrix prevents leaching out of the indicator molecules from the fingernail sensor toward such repeated use. The limited narrow working pH range of a single pH indicator has been addressed by multiplexing three different pH indicators: bromothymol blue (pH 6.0–7.6), bromocresol green (pH 3.8–5.4), and cresol red (pH 7.2–8.8), as demonstrated for analyses of real-life samples of acidic, neutral, and basic character. The new concept of an optical wearable chemical sensor on fingernail platforms can be expanded towards diverse analytes for various applications in connection to the judicious design of the recognition layer.

A wireless potentiostat for mobile chemical sensing and biosensing

Wireless chemical sensors are used as analytical devices in homeland defence, home-based healthcare, food logistics and more generally for the Sensor Internet of Things (SIoT). Presented here is a battery-powered and highly portable credit-card size potentiostat that is suitable for performing mobile and wearable amperometric electrochemical measurements with seamless wireless data transfer to mobile computing devices. The mobile electrochemical analytical system has been evaluated in the laboratory with a model redox system – the reduction of hexacyanoferrate(III) – and also with commercially available enzymatic blood-glucose test-strips. The potentiostat communicates wirelessly with mobile devices such as tablets or Smartphones by near-field communication (NFC) or with personal computers by radio-frequency identification (RFID), and thus provides a solution to the ‘missing link’ in connectivity that often exists between low-cost mobile and wearable chemical sensors and ubiquitous mobile computing products. The mobile potentiostat has been evaluated in the laboratory with a set of proof-of-concept experiments, and its analytical performance compared with a commercial laboratory potentiostat (R2=0.9999). These first experimental results demonstrate the functionality of the wireless potentiostat and suggest that the device could be suitable for wearable and point-of-sample analytical measurements. We conclude that the wireless potentiostat could contribute significantly to the advancement of mobile chemical sensor research and adoption, in particular for wearable sensors in healthcare and sport physiology, for wound monitoring and in mobile point-of-sample diagnostics as well as more generally as a part of the Sensor Internet of Things.

日常ケアのためのウエアラブル化学センサ

日常ケアのためのウエアラブル化学センサ

Freestanding chemiresistive polymer composite ribbons as high‐flux sensors

AbstractChemiresistive polymer composite ribbons that function as chemical detectors were produced from solution‐cast films of polymers and carbon composites. An array with multiple polymer sensor threads was exposed to dimethyl methyl phosphonate, a nerve agent simulant, and different interferents in the vapor phase. Principal component analysis was used to differentiate between the analytes. The response of the ribbon sensors as a function of the carbon composite and the host polymer source was investigated. The freestanding threads/sensors were mounted into a cell perpendicular to the gas flow to provide little pressure drop and were imbedded into fabrics to provide an example of a small, low‐cost, wearable chemical sensor. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Fibers and Fabrics for Chemical and Biological Sensing

Wearable sensors can be used to monitor many interesting parameters about the wearer’s physiology and environment, with important applications in personal health and well-being, sports performance and personal safety. Wearable chemical sensors can monitor the status of the wearer by accessing body fluids, such as sweat, in an unobtrusive manner. They can also be used to protect the wearer from hazards in the environment by sampling potentially harmful gas emissions, such as carbon monoxide. Integrating chemical sensors into textile structures is a challenging and complex task. Issues which must be considered include sample collection, calibration, waste handling, fouling and reliability. Sensors must also be durable and comfortable to wear. Here, we present examples of wearable chemical sensors that monitor the person and also his/her environment. We also discuss the issues involved in developing wearable chemical sensors and strategies for sensor design and textile integration.

Wearable chemical sensors and biochemical gas sensors (bio-sniffers) by a soft-mems approach

Des dispositifs et des procedes micro-electromecaniques souples (Soft-MEMS) sont necessaires pour le diagnostic medical et pour des mesures physiologiques. Plusieurs types de detecteurs chimiques portables formes de dispositifs micro-electromecaniques souples ont ete construits par des techniques de microfabrication sur des films de polymeres fonctionnels, pour doser des substances biochimiques. Le detecteur d'oxygene portable (epaisseur : 84 μm) a ete etalonne pour l'oxygene dissous entre 0 et 80 mg/l, et a ete utilise avec succes pour suivre la pression d'oxygene transcutanee en appliquant le dispositif sur la peau de l'avant-bras. La conductivite du liquide lacrymal a pu etre mesuree en appliquant un detecteur portable sur le cul-de-sac temporal inferieur d'un sujet humain, ce qui a permis de mesurer la concentration en electrolytes et la vitesse de renouvellement dans les larmes pour des volontaires sains normaux et pour des patients souffrant de secheresse oculaire. Pour une approche douce et non-invasive, des detecteurs biochimiques de gaz (bio-sniffers) pour l'ethanol et l'acetaldehyde en phase gazeuse ont ete developpes en utilisant une membrane a enzyme immobilisee et une cellule de reaction comportant des compartiments pour les phases gazeuse et liquide separes par un diaphragme a membrane poreuse. La monooxygenase a flavine (FMO, une des enzymzes de metabolisation des drogues) a aussi ete utilisee pour construire des dispositifs a biodetecteurs de gaz pour la trimethylamine, le methylmercaptan, etc, pour des mesures douces (non-invasives). Les changements de concentration de l'ethanol dans l'haleine apres ingestion ont pu etre mesures par un biodetecteur de gaz de type baguette. La technique des biodetecteurs de gaz devrait contribuer au developpement d'un systeme de nez intelligent.

Wearable chemical sensors for physical applications

Wearable chemical sensors for physical applications

生体モニタリング用ウエアラブル化学センサに関する研究

生体モニタリング用ウエアラブル化学センサに関する研究